With the increasing awareness of the importance of sustainable and healthy work environments, green office buildings have gained prominence due to their potential to enhance well-being and productivity. However, limited research has focused specifically on the cognitive effects of these buildings on employees. Hence, this research aims to investigate the impact of green office buildings on employees' cognitive functions, including attention, memory, problem-solving, and task completion. The study employs a standardised survey to assess cognitive function. A sample of 502 employees working in green (n = 261) and conventional office buildings (n = 241) were recruited. The survey also gathered data on employees' perceptions of their work environment, to gain in-depth information on indoor air quality, and the comfort level of visual, acoustic, and thermal conditions. The results showed that employees in green offices reported significantly higher mean scores on the test of perceived attention and problem-solving than those in conventional offices (p < 0.05). In addition, employees in green offices exhibited a 10% increase in their average cognitive functioning scores compared to conventional buildings. This was combined with a higher score of overall perceived comfort. The findings highlighted a positive association between working in green buildings and employees’ cognitive function.